The present invention relates to precision signal sources and more particularly to a power source which will accurately supply preselected voltage and current waveforms, precisely related in time, for use in the calibration of electrical measurement equipment, e.g., power meters.
In order to calibrate watt-hour meters and other power measurement devices, it is necessary to provide precisely defined reference waveforms, current and voltage, which are also precisely related in time or phase. Heretofore, power calibration sources have been implemented as essentially analog devices using voltage controlled oscillators and precision feedback systems to maintain the desired waveform accuracy and phase relationships. While various systems employing digital techniques have been proposed for other types of precision sources, e.g., for the measurement of core losses in transformers and the like, these prior art systems have not been readily adaptable or sufficiently precise for use as precision power calibration standards.
Among the several objects of the present invention may be noted the provision of novel apparatus for generating a precisely defined waveform; the precision of such apparatus which will generate both current and voltage waveforms; the provision of such apparatus which will generate current and voltage waveforms in precisely defined phase or time relationships; the provision of such apparatus which will generate precision waveforms of preselectable wave shape; the provision of such apparatus which is easily adjustable as to operating parameters, including amplitude and phase; the provision of such apparatus which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.